Numerous studies from this laboratory have investigated the interaction of insulin with circulating mononuclear cells. It has been demonstrated that obese diabetic individuals have a deficiency in insulin receptors and these are reversed by appropriate diet. Further, numerous other diseases of receptor deficiency have been identified. The present project involves studies on in vivo and in vitro states of insulin-dependent diabetes mellitus (IDDM) and glucocorticoid excess. We have attempted to characterize the insulin receptor of the human erythrocyte.